The present invention relates to a motor-operated valve incorporated in a refrigerating cycle system such as a refrigerator, an airconditioner, and a freezer for controlling a flow rate of a refrigerant or for opening and closing a flow passage.
Conventionally, in a refrigerating, freezing, or air-conditioning cycle of a refrigerator, a freezer, an airconditioner of a heat-pump type, or the like, a refrigerant line has a motor-operated valve for controlling a flow rate of a refrigerant or for switching flow passages. For example, a motor-operated valve used in a heat-pump type airconditioner particularly often operates to adequately control a room temperature. Such a conventional valve generates a loud noise in operation, so that the valve is not desirably positioned in a room but is positioned around an outside machine having a heat exchanger. Thus, the expansion valve for adjusting a flow rate of a refrigerant to control a room temperature is positioned in the outside apart from an in-room apparatus. This is disadvantageous for a control performance such as responsiveness of the heat exchanger. Furthermore, a pipe line for delivering a refrigerant from the in-room apparatus to an outside machine must be located in the outside under a high temperature condition, while the refrigerant in the pipe line is cooled by its expansion in the expansion valve in a cooling operation. Even with an insulation layer, a large quantity of heat radiates from the pipe line into the atmosphere, reducing the efficiency of the heat exchanger.
In addition, an apparatus other than such air conditioners, for example a refrigerator, often uses an expansion valve which is more expensive than a conventional refrigerant flow control device such as capillary tubes. That is because a recent refrigerator has a larger capacity and requires a precise temperature control for a freezing space and a vegetable space thereof. Such a refrigerator is disposed in a room, so that a motor-operated valve such as an expansion valve is positioned in the room. A noise generated from the motor-operated valve must be reduced as much as possible.
FIG. 22 shows a motor-operated valve used in such above-mentioned apparatuses as an example. The valve has a valve main body 60 provided with a first opening 62 communicating with a first passage 61 in a downward axial direction thereof, a second opening 64 communicating with a second passage 63 at a side portion thereof, and a valve chamber 65 communicating the first opening 62 with the second opening 64. On a top portion of the valve main body 60, there is disposed a housing 67 having a bottom cover 66. The housing 67 is mounted with a magnet 68 on an outer surface thereof and accommodates a resin-made rotor 71 having a central pin 70. The rotor 71 is extending downward together with the pin 70 to be inserted into the valve chamber 65. At a lower end of the pin 70, there is provided a needle valve 72 moved forward and backward relative to the first opening 62.
The needle valve 72 has an upper, outer periphery slidably laterally engaging with an inner surface of the valve chamber 65 to constitute a lower guide wall 79. The rotor 71 has a lower, downwardly extended portion 73 formed with an external thread 74, and the valve chamber 65 has an inner surface formed with an internal thread 75 engaging with the external thread 74. Thereby, the rotation of the rotor 71 moves itself upward and downward, since the rotor 71 is engaging with the fixed internal thread 75 through the thread engagement, so that the needle valve 72 integral with the rotor 71 moves upward and downward relative to the first opening 62 to control a fluid flow passing therethrough.
The pin 70 has an upper end 76 projecting from the rotor 71 and opposed to an inner surface of a top portion 77 of the housing 67. The rotor 71 has an outer periphery opposed to an inner periphery of the magnet 68. The inner periphery defines an upper, eccentric, first cylinder 78 and a lower, reduced-diameter, second cylinder 80. The eccentric first cylinder 78 engages the rotor 71 with the magnet 68 not to rotate them relative to each other.
The magnet 68 has a lower end portion extending to an outer periphery of 84 of the valve main body 60. The lower end portion has a rotor support 87. The rotor support 87, as illustrated in FIG. 22, can abut against a stopper pin 88 secured to the valve main body 60. The magnet 68 has an upper end portion defining an upwardly extended portion 90 which can abut against an upper stopper 92. The upper stopper 92 is an outer peripheral, downwardly extended member of a stopper mechanism 91 secured on an inner peripheral wall of an upper cover of the housing 67. The housing 67 has an outer cylindrical surface mounted with coils 93 communicating with an outer device via a connector 94.
In a motor-operated flow control valve 95 having one thus configured needle valve, the application of an electrical power to the magnet 68 rotates the rotor 71. Thereby, the engagement between the external thread 74 formed in the extended portion 73 of the rotor 71 and the internal thread 75 formed in an inner wall of the valve chamber causes the rotation of the rotor 71 to move upward and downward. This moves vertically the needle valve 72 formed in the pin 70 secured on the rotor 71, which changes an open area of the first opening 62 to control a flow rate of a fluid passing therethrough.
When the needle valve 72 fully closes the first opening 62, the rotor support 87 of the magnet 68 abuts against the stopper pin 88 to mechanically stop the rotation of the rotor 71 regardless of a power pulse supply to the coils. Meanwhile, when the needle valve 72 fully opens the first opening 62, the upwardly extended portion 90 of the magnet 68 abuts against the upper stopper 92 of the stopper mechanism 91 so that the rotor 71 also stops.
The motor-operated valves of various types each having a construction other than the above-mentioned one have been used in a freezing cycle system or the like. For example, Japanese Patent Laid-open No. H. 4-68510 discloses a rotor having a rotation stopper mechanism which has been widely used. Referring to the mechanism, a case of a motor-operated valve has an upper cover fitted with a downwardly extended central rod. The central rod is surrounded by a helical guide ring which vertically slidably engages with a slider. The slider has an outer end engaging with a stopper rod raised from the rotor.
The conventional motor-operated valve illustrated in FIG. 22 has the rotor having upper and lower projections abutting against the stoppers provided on a case of the rotor. This arrangement stops the rotation of the rotor when the needle valve is in the fully open state or in the fully closed state. However, the motor-operated valve requires the upper and lower stoppers, which increases the number of parts and causes an increase in an assembling man-hour of the valve. This is a disadvantage of the motor-operated valve. The rotation stopper mechanism disadvantageously requires a further increased number of parts and a further increased assembling man-hour, because the mechanism has the central rod wound by the helical guide spring and the stopper rod raised from the rotor.
In addition, the valve element stops in the fully open and closed positions by abutting the members rotating with the rotor against the stoppers. However, since the engaging threads may have a backlash therebetween, the stopping states of the valve element may not be sufficient.
Furthermore, the stopping members rotating with the rotor abut against the stoppers which are positioned radially apart from the central axis of the rotor. This disadvantageously generates a larger chattering noise when the stopping members hit the stoppers by pulses alternately turning the rotor in the normal or reverse direction around the stopping position, since the stopping members are accelerated in the circumferential speed by the radial distance of the stopping members.
Such alternate pulses are temporarily provided to the rotor when the fully open or closed condition of the needle valve is initialized, or even when the needle valve is in a normal fully open or closed condition, since power pulses may be still supplied in the fully open or closed condition of the needle valve. This generates such a loud noise of the abutment of the stoppers.
Furthermore, the stoppers of the rotation stopper mechanism have problems in dimension control and durability, which decreases the reliability of the motor-operated valve and causes an increased manufacturing cost of the motor-operated valve.
Moreover, the above-mentioned motor-operated valve has the rotor formed with the thread which engages with the opposing thread formed in the valve main body. Thereby, the rotation of the rotor causes the needle valve to move linearly, and the rotor is fully supported by the thread engagement portion. This construction causes a vertical vibration of the rotor due to a backlash of the threads, and the rotor also may deviate from its central axis, resulted in generation of a noise.
Another motor-operated valve used in an airconditioner apparatus has been proposed. The motor-operated valve has a rotor and an actuating shaft which engage with each other through threads so that the rotation of the rotor causes the actuating shaft to move linearly. The actuating shaft moves a valve element vertically but is a body formed separately from the valve element. The rotor is supported not to move vertically, and the valve element is moved vertically but is not rotated. However, the motor-operated valve still has stoppers to stop the rotation of the rotor at fully open and closed positions of the valve element. The motor-operated valve has the disadvantages of an increased number of parts, an increased assembling man-hour, a less durability, etc.
Therefore, an object of the present invention is to provide a motor-operated valve which can stop appropriately a needle valve element without an additional stopping mechanism. The motor-operated valve has the advantages of a less number of parts, a reduced vibration, and a reduced noise.
Another object of the present invention is to provide a motor-operated valve which has a flat spring between a bearing and a needle valve to eliminate an impact noise otherwise generated when the needle valve directly abuts against the bearing.
For achieving the objects, a motor-operated valve according to the present invention includes a rotor having a shaft formed with an external thread and a needle valve element. The valve element has a valve head at one end portion thereof and an internal thread engaging with the external thread at another end portion. The valve element also has a joining portion for joining the valve head to the internal thread. The motor-operated valve also includes a main valve body having a guide portion which stops rotation of the valve element but allows an axial movement of the valve element. The shaft has an upper end rotatably supported by a supporting portion provided on a top wall of a valve housing, while a lower end of the shaft is rotatably supported by a bearing secured to the main valve body.
Another motor-operated valve according to the present invention includes a rotor having a shaft formed with an external thread and a needle valve element. The valve element has a valve head at one end portion thereof and an internal thread engaging with the external thread at another end portion. The valve element also has a joining portion for joining the valve head to the internal thread. The motor-operated valve also includes a main valve body having a guide portion which stops rotation of the valve element but allows an axial movement of the valve element. The main valve body has a valve seat. The shaft has an upper end supported by a supporting portion provided on a top wall of a valve housing, while a lower end of the shaft is rotatably supported by a bearing secured to the main valve body.
The internal thread may be made of a synthetic resin material.
The joining portion comprises a pair of opposing rods. The bearing has a guide for slidably guiding the rods, and the guide stops the rotation of the valve element. The bearing has a rotation stopper projection engaging with the valve element. The bearing also has a support recess receiving the lower end of the shaft to receive a thrust force of the shaft. Furthermore, the bearing has a bearing bush made of an elastic material. The bush has a hole receiving the lower end of the shaft. The bush also has a thrust receiving portion protruding from each surface of the bearing. The bearing may be a flat plate made of a synthetic resin material and having a central hole receiving the lower end of the shaft. The bearing may have a spring upwardly urging the lower end of the shaft.
The valve element has a recess formed on an outer peripheral surface thereof. In the recess, there is provided a slider made of a low friction material. The shaft has an end directly engaging with a recess formed on a top wall of a valve housing. Alternatively, the shaft may have an end rotatably supported by a shaft supporting piece, and the shaft supporting piece has a projection engaging with a recess formed on a top wall of the valve housing. Between the bearing and a top surface of the rotor, there may be provided a compressed spring for urging downward the rotor. Between the valve element and the valve main body, there may be provided another compressed spring urging downward the valve element. Between the valve element and the valve main body, there may be provided further another compressed spring urging upward the valve element. The external thread may be provided separately from the valve element to be integrated on the valve element afterward. The needle valve may be provided separately from the valve element to be integrated on the valve element afterward. The valve head may have a disengagement preventing member at a top portion thereof and may have a spring receiving portion at an intermediate portion thereof. The valve head is disposed at a lower end of the valve element. Between the spring receiving portion and the lower end of the valve element, there is provided further another compressed spring. The joining portion may have an upper end shoulder abutting against a flat face of the bearing when the valve head is fully closed, so that the rotation of the rotor stops.
The internal thread may be preliminarily formed as an insert from the same synthetic resin material as the valve element. The bearing may be made of a sintered metal.
Between the bearing and the valve head, there may be provided a plate piece having an elastic character for urging downward the valve element at an initialization position of the valve element.